Cosmetic pencils are commonly used for the application of eye shadow, eye liner, or lipstick, and are composed of an outer barrel or sheath and an inner core of a wax-like cosmetic material. Traditionally, the barrel has been formed of wood by gluing together two longitudinally split halves, and because of this method of manufacture, hot melted cosmetic core material could not be poured directly into the barrel or the heat would destroy the glued joint in the wood barrel. Consequently, the traditional practice has been to insert the pre-formed rods of the core material into the tubular wood barrel which is a difficult processing operation. As a result, only harder type core materials are usable with a wood barrel.
As a further problem, the wood barrels are produced from tight grain cedar which is only available in certain parts of the world, and recently, the quantities of this type of cedar have been extremely limited.
When using cosmetic materials that incorporate a volatile solvent, the solvent can "wick through" or penetrate the wood barrel. To prevent the loss of solvent, it has been necessary in the past to line the barrel with an impervious material, such as metal foil, and this further increases the cost of manufacture.
Some wood barrels, depending on the characteristics of the wood, are difficult to sharpen with a conventional sharpener and tend to break away in small fragments which can embed in the cosmetic core, resulting in a scratchy application to the skin.
Wood barrels are also sensitive to heat and humidity conditions, and may warp or split under high humidity.
As the wood barrels are normally made of cedar, the cedar odor tends to distort any fragrances incorporated in the cosmetic core material.
More recently, cosmetic pencils have been introduced into the market utilizing a polyethylene-type sheath or barrel. The polyethylene barrel has distinct advantages over the wood barrel in that it is more resistant to heat and humidity conditions and can be more easily processed or manufactured.
Though the polyethylene-type barrel can be sharpened with a conventional pencil sharpener, it has been observed that the shavings have a brittleness that results in plastic particles embedding themselves in the core product which affects the application. In contrast to the wood barrel, the polyethylene-type barrel is odorless, so that it is possible to use fragranced products whose odor will not be distorted.
However, it has been observed that the polyethylene-type barrel is subjected to stress cracking at temperatures in the range of 40.degree. C. to 50.degree. C., with the result that volatile solvents, that may be contained within the cosmetic core, can escape to the atmosphere, resulting in a drying out of the cosmetic composition. In addition, the commonly polyethylene-type barrel is pervious to some materials, so that they cannot be successfully incorporated in the barrel.
As a further disadvantage, the conventional polyethylene-type barrel is not compatible with many colorants, particularly pearlescents, with the result that the polyethylene-type barrel is limited by the colors that can be utilized.